Battery terminal bolts dissovling.

[rickpaulos]

Rider mower, 12v battery.

I have had to replace the bolts many times. These are the latest. The negative terminal bolt is fine, the positive terminal bolt is dissolving away where it is exposed to air. I tried using stainless steel bolts last time but they don't last either. I think I used some of that battery post grease they sell at the auto stores. Yesterday when the mower would not start, I took the cover off and found the positive post covered under a mount of red foamy goop. What's going on? I think I tried brass bolts & nuts before with similar results. Would copper bolts help? I've had to replace the positive battery cable before but it does last much longer than the bolts. The terminals are normal lead covered, the cable end is a regular electrical terminal. Is this from overcharging? What should the voltage be? I think it is very strange that the parts of the nuts & bolts exposed to the air are the parts that are dissolving. You can see the "before & after" effects. (negative bolt & positive bolt).

IMG_1375 by rickpaulos, on Flickr

IMG_1376 by rickpaulos, on Flickr

 

[motoman]

Tell us how much time passes before replacements. Many would not be concerned with what the pictures show, but sounds like you are very diligent. A couple tricks I use. Sometimes bathe the outside of your battery with a mixture of baking soda and water and dry it. Keep the battery top dry. Metal hold -down brackets and screws are conductors and tend to promote corrosion. I make my brackets out of plastic. Try cutting one out of large dia PVC pipe. Stopping corrosion entirely is impossible. There are something like 11 kinds of corrosion. Most common is with liquid electrolyte (water . acid) connection, but moist air also serves. It does seem you have an active case.

 

[rickpaulos]

Tell us how much time passes before replacements. Many would not be concerned with what the pictures show, but sounds like you are very diligent. A couple tricks I use. Sometimes bathe the outside of your battery with a mixture of baking soda and water and dry it. Keep the battery top dry. Metal hold -down brackets and screws are conductors and tend to promote corrosion. I make my brackets out of plastic. Try cutting one out of large dia PVC pipe. Stopping corrosion entirely is impossible. There are something like 11 kinds of corrosion. Most common is with liquid electrolyte (water . acid) connection, but moist air also serves. It does seem you have an active case.

I've had the mower about 20 years. time between? Hum, I don't remember exactly, a couple years perhaps. The battery sits on rubber pads and is held down by a bolt with a rubber cover. I have replace the battery 5 or 6 times since the mower was new. Each new battery seems to last less time.

 

[Mad Mackie]

This is one of the reasons that I prefer a sealed battery. If a charging system is putting out higher voltage than it should, then corrosion of the battery bolts will happen sooner than normal. I generally use stainless steel bolts, washers and nuts, because I have a lot of stainless steel hardware around having been a marine mech in the past.
Battery connecting involves dissimilar metals no matter what and add sulphuric acid to the mix and corrosion of the least noble metal will happen. Also the copper terminals get ate up with corrosion. Just one of those frequent maintenance items that need to be addressed.

 

[bertsmobile1]

It is called galvanic corrosion and is perfectly normal.
Small amounts of acid fume condense on the bolts and when they get damp ( dew ) corrode the bolts.
That is why you grease these bolts.
I use a product called liquid electrical tape and paint the terminal, nut & bolt but leave the last 1/4" bare for jump starting or taking measurements.